This relevant anatomy of the thoracic outlet is useful in understanding thoracic outlet syndrome.
In thoracic outlet syndrome, there’s compression or irritation of brachial plexus elements
or there can also be involvement of the subclavian vein or the subclavian artery. What are some
of the structural causes of thoracic outlet syndrome and there are several. The first structural
cause could be the presence of cervical ribs. Another structural cause could be the presence
of fibrous bands running within this region compressing some of these structural outlet elements.
If there’s hypertrophy of the scalene muscles that could then compress or put pressure on the
elements passing through the interscalene triangle. So, brachial plexus trunks could be involved
here or the subclavian artery could be involved. Another potential cause is the presence of
anomalous muscles in this particular region. Then lastly, it’s also possible that the Pancoast tumor
which is a long tumor could pass superiorly and start to involve structures of the thoracic outlet.
More specifically, it would be the inferior most structures of the brachial plexus to be involved first.
That would be the inferior trunk. The roots that joined to form the inferior trunk are the C8
and T1 spinal roots. What are some of the symptoms then of thoracic outlet syndrome?
One symptom is numbness and pain along the medial arm, forearm, and fourth and fifth digits.
This would be due to the involvement of the inferior trunk region of your brachial plexus, the C8
and the T1 dermatomal areas that supply the skin of these regions. Another symptom
is muscle weakness in the hand. The intrinsic muscles are innervated by T1. So, if there’s
compression of the inferior trunk then you can also have muscle weakness of these intrinsic
muscles. It’s also possible if there’s involvement of the subclavian vein that you would decrease
venous return to the heart. If that were to occur then you would have swelling of the arm
due to that insufficient venous return. Then the last potential symptom would be due to involvement
of the subclavian artery. So, if it becomes compressed, narrowed, stenotic then that can lead to
pallor and coldness of the upper extremity. This was the image that began this lecture with the
introduction. This X-ray is the same image that was in the introduction slide. The purpose of this
radiograph is to demonstrate the bilateral cervical ribs. Again, this is one of the potential
structural causes of thoracic outlet syndrome. So if we take a look, here is C7 right in through
here. Here, you can see a cervical rib and here is the lateral most point of that cervical rib.
You can see the opposite cervical rib bending around right in this particular area.
So again, these have the potential to compress thoracic outlet components.